1. Field of the Invention
This invention relates to a pressure-sensitive adhesive structure (or structural body).
2. Description of the Prior Art
Pressure-sensitive adhesive structures comprising a substrate and a pressure-sensitive adhesive layer (a layer comprising a pressure-sensitive adhesive) laminated on both sides each or one side of the substrate, a release agent layer, and optionally further a laminating substrate, as exemplified by pressure-sensitive adhesive tapes and pressure-sensitive adhesive labels, are used in various purposes. In recent years, as pressure-sensitive adhesives used in the pressure-sensitive adhesive structures, silicone pressure-sensitive adhesives mainly composed of dimethylpolysiloxane (hereinafter referred to as dimethylpolysiloxane-based pressure-sensitive adhesives) are used in extensive use because of their excellent heat resistance, cold resistance, chemical resistance, electrical insulating properties and nontoxicity.
However, because of a very strong adhesion, the dimethyl polysiloxane pressure-sensitive adhesives require an excessively large peel force when the pressure-sensitive adhesive layer is peeled from the release agent layer in the case of conventional pressure-sensitive adhesive structures, and the peel force of the pressure-sensitive adhesive layer from the release agent layer remarkably increases particularly when the pressure-sensitive adhesive structures are stored for a long period of time, so that the pressure-sensitive adhesive layer or release agent layer may be readily destroyed when the pressure-sensitive adhesive layer is peeled from the release agent layer. Or components in the release agent layer may migrate into the pressure-sensitive adhesive layer to reduce adhesion possesed by the pressure-sensitive adhesive layer during a long period storage. As the results, the structures may often become of no use as pressure-sensitive adhesive structures.
Now, an object of this invention is to provide a pressure-sensitive adhesive structure that may require a small peel force and have good release properties even when the dimethylpolysiloxane-based pressure-sensitive adhesives are used, and can retain its good release properties with a high stability even after its storage for a long period of time.